The invention relates to a self-closing pliers which can be actuated by one hand, having two pliers legs which are connected to one another by means of an articulation bolt, it being the case that a pliers mouth is formed above the crossover region of the pliers legs and handle sections are formed on the pliers legs below the crossover region, it being the case that one of the pliers legs, which can be adjusted relative to the other pliers leg in the crossover region in order to change the size of the pliers mouth, has a free space which is penetrated by the other pliers leg, or the non-adjustable pliers leg is penetrated by the adjustable pliers leg, and it being the case that, furthermore, the pliers legs are connected via a regulating element and a spring drive, which biasses the pliers mouth into an open position, which open position is produced automatically under spring loading once the handle sections have been relieved of loading, it being the case that, moreover, in a first movement section of the spring drive, the pliers-mouth jaws move towards one another and, in a second movement section, a catch of the articulation bolt engages in a latching toothing formation, whereupon forced rotation of the movable pliers-mouth jaw about the articulation bolt can be carried out.
It is an object of the invention to improve pliers of the generic type in structural and functional terms.
This object is achieved first and foremost, in the case of such pliers having the features of claim 1, this being based on the fact that the spring drive comprises a spring which is supported on the two pliers legs and is formed so as to effect both expansion of the pliers legs into a spaced-apart position and displacement of the movable pliers leg into the largest opening position of the mouth, with rotation of the pliers leg by said spring, it being the case that a rotary support of the spring is formed on the pliers leg on at least one side and on this side, in the non-actuated state, the spring butts against a rotary stop formed on the pliers leg, it being the case that, upon displacement of the movable pliers leg into a workpiece-gripping closed position of the mouth, the spring is released from the rotary stop only with the actuation of force when the pliers-mouth jaws are butting against the workpiece. This gives a self-contained force system integrated in a regulating element. The spring is prestressed such that, when the pliers are released, the movable pliers leg snaps into the open position. It is advantageous then for the regulating element to be formed by a spring which is supported on the two pliers legs and, at the same time, biasses the pliers mouth into the open position. The rotary stop is formed as a supporting flank. This can also easily be taken into account in terms of moulding technology. It is further proposed that the leg spring has two spring sections of different stiffnesses. This results in an operational sequence of the spring drive. The invention also proposes that the different stiffnesses are achieved by different lengths of the spring sections. It is further provided that the spring is subdivided into the two spring sections by means of a spring coil. Such a spring coil, which may be formed with a plurality of layers, contains an adapted stored spring-force reserve. It is further provided that the points of articulation of the spring are disposed at different spacings from the pliers mouth. In specific terms, this takes place such that the point of articulation of the longer spring section is closer to the pliers mouth. In addition, one configuration is implemented to the effect that the shorter spring section is supported at a location beyond which it is not possible to pass in the direction of the pliers mouth. Precautions are taken here for a capacity for rotary movement of the shorter spring section at the point of articulation to be limited in angular terms. It is provided here that the angle of rotation is an acute angle. It is further provided that the spring has two coils located one beside the other. This gives an even more balanced force system, in particular a good spring characteristic.
In the case of pliers having the features of the preamble of claim 1, it is advantageous for the regulating element to be made up of a spring section and a rigid section. Like the short spring section, this rigid section is also supported at a location beyond which it is not possible to pass in the direction of the pliers mouth. In the case of this solution, it is also proposed that the spring section is formed by a helical spring. This may be a leaf spring with an end turn which encloses a central non-round cross-section in a slip-free manner. It is advantageous here for the rigid section to be a link, at one end of which the spring element is fastened in the manner described and the other end of which is disposed rotatably on the pliers leg, in this case too, in turn, with the proviso of being supported at a location beyond which it is not possible to pass.
It is advantageous in terms of stability if the link is formed in a pair and a free space for the spring and the spring fastening is left by virtue of the two links being spaced apart. It is advantageous here for the spring fastening to be achieved by a carrying pin which penetrates the group of turns of the spring coil and connects the links. The spring is thus secured reliably. It is favourable here, moreover, for the spring section of the spring in the form of a rotary leg spring, said spring section being directed towards the rigid section, to be supported on the rigid section. The support may be formed by a tongue cut out of the link; alternatively, the support may be formed by a pin which likewise connects the links. It is then proposed that the spring is supported on two rigid sections which are connected to one another in the manner of a toggle lever. In order to assist the biassing force of the spring, it may further be proceeded such that a second spring which is disposed on the handle section preloads one of the rigid sections in order to produce a straightened-out position of the rigid sections in relation to one another. As regards the abovementioned straightened-out position, it may be said that, in the straightened-out state, the two rigid sections enclose between them an angle of less than 180xc2x0 which opens on the mouth side. This prevents a dead-centre position of the rigid sections, which are connected to one another in the manner of a toggle joint, between the points of articulation of the pliers legs. A further feature is that the rigid section connected to the further spring is double-armed. The spring action thus takes place in the same direction as the other, first spring.
Pliers with a minimum number of components are achieved if the spring is formed as a clip spring with clip-spring arms and a clip-spring bend, the clip-spring arms being supported on one of the pliers legs and the clip-spring bend being supported on another of the pliers legs. The spring and regulating elements are configured integrally with one another. The clip-spring arms or the clip-spring bend are/is supported by means of a rigid section mounted rotatably on a pliers leg. The spring prestressing of the spring drive and the spring force itself are applied here in that the freely projecting clip-spring arms are supported rotatably on a rigid section or a pliers leg via different axes of rotation. The spacing between the axes of rotation is converted into the desired spring force by the pliers legs being pivoted. The clip-spring arms are formed to be of different lengths. This, in conjunction with the spaced-apart axes of rotation, results in a torsional action in the clip-spring bend and also in a specific curvature of the clip-spring arms. The clip-spring arms may be curved, for example in the manner of an already slight precurvature. The curvature is formed to be concave in the direction facing the pliers mouth. It is also proposed that formed on the rigid section is a stop which interacts with the spring when the spring drive is in the straightened-out position. In addition, it may be advantageous for the clip-spring bend to be of helical form. This makes it possible to achieve a bearing eyelet at the same time. The bearing eyelet is not made to undergo a torsional action. Moreover, it is provided that the clip-spring bend is supported in a longitudinally movable manner on a pliers leg. A straightforward association is achieved here in that the clip-spring bend is accommodated in a slot of a pliers leg. In order for it to be possible to maintain, by straightforward means, the sequence of the mouth being closed and applying a forceful grip, it is proposed that the support of the clip-spring bend is of profiled form with an initial supporting surface which is inclined in relation to the longitudinal direction of the pliers leg and grips below the clip-spring bend. An alternative feature consists in that a tension spring acting in the longitudinal pliers-leg direction acts on the clip-spring bend.